Mu'adh ibn Jabal was a young Ansari of Madinah, foremost among the Companions in knowledge of what is lawful and unlawful. Later the Messenger of Allah ﷺ sent him to Yemen to teach people the religion.
❝ HadithOne day the Messenger of Allah ﷺ took Mu'adh by the hand and said: O Mu'adh, by Allah, I love you. Then he said: O Mu'adh, never leave saying after every prayer: Allahumma a'inni 'ala dhikrika wa shukrika wa husni 'ibadatik — O Allah, help me to remember You, to thank You, and to worship You well.Sunan Abi Dawud 1522 · Sahih (al-Albani)
❝ HadithSending him to Yemen, the Messenger of Allah ﷺ said: you are going to a people of the Book; first call them to bear witness that there is no god but Allah; if they accept, tell them of the five daily prayers; then of zakah, taken from their rich and given to their poor. And beware the prayer of the wronged, for there is no barrier between it and Allah.Sahih al-Bukhari 1496 · Sahih